A method of laser coagulation of vessels by argon laser, radiation wavelength 488-514 nm is known [“Laser surg. Med.”, 1992, vol. 12, pp. 246-253. “Applied laser medicine”. Edited by H. P. Berlien, G. Y. Muller, pp. 326-327, 1997].
The medical effect in laser coagulation of vessels by argon laser, radiation wavelength 488-514 nm is based on the fact that argon laser radiation is well absorbed by hemoglobin, leading to temperature increase inside the blood vessels resulting in coagulation of the blood vessels.
But the radiation wavelength with laser coagulation of vessels by argon laser, radiation wavelength 488-514 nm is not able to penetrate deep into blood vessels, hence the method cannot be used for the coagulation of big vessels. Moreover, the argon laser radiation is also well absorbed by other skin constituents resulting in-the overheating of surrounding tissue and diminishes the medical effect even in coagulation of small vessels.
An additional method of blood vessels coagulation involves use of YAG:Nd laser operating in the mode of the second harmonic generation is also known in the art [U.S. Pat. No. 5,558,667, publication date 24 Sep. 1996, “Method and apparatus for treating vascular lesions”.
YAG:Nd laser radiation with the wavelength of 532 nm, pulse duration of 0.5-10.0 ms and energy density of 10-20 Joules/cm2 is also well absorbed by hemoglobin thereby allowing coagulation of small blood vessels. The disadvantage of the YAG:Nd laser radiation method lies in the fact that beside hemoglobin other constituents of soft tissue also absorb the radiation and the skin penetration deepness is not sufficient to coagulate the vessels without causing damage of the surrounding soft tissue.
An additional method for coagulation blood vessels involves use of dye laser radiation by pulses with the wavelength of 585 nm [Treatment of Vascular Lesions in Pigmented Skin with the Pulsed Dye Laser, “Laser surg. Med.”, 1992, suppl. 4, pp. 65-74].
Such wavelength (e.g., 585 nm) allows deeper penetration into soft tissue at the expense of lesser absorption by various skin constituents. The absorption effectiveness of radiation with a 585 nm wavelength by hemoglobin is less than that of the argon and the second harmonic YAG:Nd lasers, though it is compensated that the radiation penetrates deeper inside the vessel causing blood coagulation in greater volumes. Owing to this fact, methods using radiation with a 585 nm wavelength allows coagulation of bigger vessels. However, to effectively heat the whole vessel volume it is necessary to use greater energies so as to avoid partial blood coagulation, which will not provide sufficient vessel walls heating and may cause displacement of the coagulated blood portion during blood circulation. In addition, the use of high-energy radiation in the given wavelength range provokes substantial overheating of the surrounding tissue, which may result in irreversible changes in them.